Irrigation systems typically comprise a plurality of separate stations each having one or more sprinklers supplied by a common valve. An irrigation controller causes the stations to run or operate in accordance with a schedule or program stored in the controller. However, it is usually not necessary for irrigation to take place when it is raining. Various rain switches are known which override the controller's commands and prevent any scheduled watering during rainfall. This conserves water.
U.S. Pat. No. 3,808,385 to Klinefelter discloses a prior art rain switch in which an electrical switch is wired into the irrigation control system to prevent irrigation whenever the switch opens. The switch is actuated by a plurality of hygroscopic discs which expand when wet to push on a plunger that is in contact with the electrical switch. The plunger will open and close the electrical switch.
Prior known switches are not very versatile in terms of how they can be mounted on buildings or walls. They typically also include a large number of components that can be difficult to disassemble for the purpose of repair or replacement. In addition, the electrical switch is often supported in a manner in which it is exposed to the rain water. This requires a moisture impervious sealed switch to be used, further increasing the cost and complexity of the device.